Oil Temp Relation To OATs

[Txbyker]

I've noticed my oil temps are running much higher over the last couple of months. I have had the plane 1.5 years and didnt really analyze the temps until I got an EDM730 where I can use the JPI EZTrends program. I have tracked that last 19 flights over 1 hr duration since the end of April and today I got oil temp alerts at 211 degrees on the JPI and had to trail half cowl flaps to cool it down to under 200 degrees. So here in Texas its 105 on the ground and 85 dF at 9000 feet.

My question is, does anyone know the relation of OAT to engine oil temp. For example does OAT at 10 degrees higher automatically translate to 10 degrees on the engine? Everything else checks out fine. Over the last 1.5 years of ownership I have never opened the cowl flaps in cruise to cool it down but perhaps I probably should have if I would have had the EDM warning. See graph attached. Red is max oil temp each flight and yellow is average oil temp each flight, first data point April 24th last data point today.

[jetdriven]

What kind of climb and leaning schedule do you adhere to? Are you a LOP pilot? Are your baffles and silicone baffle seals in good TIGHT shape? What altitudes do you cruise at?

Our 77  oil temp averags not quite mid green maybe in the winter, and never over ~200 indicated all year long (left edge of the "F" on the guage.   How does that correlate to your gauge?

Also, IIRC the J guage takes the reading AFTER the oil cooler. if you put the JPI probe ahead of the cooler in the stream, its going to show hotter, that oil read is not cooled yet.

It will be interesting to compare.  We are in Houston as well.

here is where ours runs at the most on a 60 degree day or less.  Again, the needle covers the left edge of the "F" on the hottest day or high altitude. never higher. :

[Earl]

I can't comment on the specific correlation but no doubt oil temps go up as OAT rises.  

[KSMooniac]

I don't have an oil temp probe on my JPI, but on hot days it does creep up there.  I haven't seen it go above the green range on the OEM gauge, but it gets close.  I'm running LOP in cruise all the time and a flight a couple of weeks ago required me to use cowl flaps intermittently to keep my CHTs under 380 dF, at 9000' and 8.0 GPH with an OAT of ~70 dF.  My vernatherm and oil cooler (and the rest of the engine build) are old and I've thought about overhauling/replacing both sooner instead of waiting for overhaul, and re-using them when I do overhaul.

[Txbyker]

I climb and lean as near 50 ROP as possible.  50 ROP at cruise.  I was able to find avg temperatures aloft with the help of my Foreflight and plotted it agains the JPI.  It looks like over 50 degrees F the avg oil temps are near 200 in my plane according to JPI.

See chart.  Grey is extrapolated temperatures aloft.  Red is the max oil temp and green is avg.  This from mid-May to yesterday.  Yesterday was a scorcher.

[jlunseth]

No dates on there. You don't suppose the progression correlates with the seasons, cooler temps in the winter, warming during spring, high in the summer?

[KSMooniac]

Quote: txbyker

I climb and lean as near 50 ROP as possible.  50 ROP at cruise.  I was able to find avg temperatures aloft with the help of my Foreflight and plotted it agains the JPI.  It looks like over 50 degrees F the avg oil temps are near 200 in my plane according to JPI.

See chart.  Grey is extrapolated temperatures aloft.  Red is the max oil temp and green is avg.  This from mid-May to yesterday.  Yesterday was a scorcher.

[jetdriven]

Russ, what is your CHT in climb and cruise? Airspeed in climb?  RPM in climb?

[jetdriven]

Quote: KSMooniac

I don't have an oil temp probe on my JPI, but on hot days it does creep up there.  I haven't seen it go above the green range on the OEM gauge, but it gets close.  I'm running LOP in cruise all the time and a flight a couple of weeks ago required me to use cowl flaps intermittently to keep my CHTs under 380 dF, at 9000' and 8.0 GPH with an OAT of ~70 dF.  My vernatherm and oil cooler (and the rest of the engine build) are old and I've thought about overhauling/replacing both sooner instead of waiting for overhaul, and re-using them when I do overhaul.

[KSMooniac]

I'm still using 380 as my soft limit, but don't sweat it too much.  The only time in 5.5 years of flying mine that it has gone over that in the climb was departing Vegas on a hot day.  Otherwise I've been able to manage it in the heat of summer by leaning further, but my last trip was bucking headwinds and I didn't want to lean any further, so I used the cowl flaps instead.

[Txbyker]

Scott, I misspoke earlier when I said I climb 50 ROP.  I try to lean out after 3000 density to as close to 100 ROP then once in cruise, 50 ROP.  Are you saying this sounds too lean?

I have been using Bob Kromers guidance.  http://www.mooneypilots.com/mapalog/powersettings.html

Byron, in cruise (8000-9000 ft, full throttle, 25", 50 ROP) I see EGT of 1300 and CHT of 330 pretty consisently avg over my last 20 flights.  

Climb out full throttle, full prop, leaning mixture I get about 750-1000 fpm at 90-100 knots up to 8000 from the best of my memory.

[Txbyker]

Quote: jlunseth

No dates on there. You don't suppose the progression correlates with the seasons, cooler temps in the winter, warming during spring, high in the summer?

[danb35]

Quote: txbyker

Scott, I misspoke earlier when I said I climb 50 ROP.  I try to lean out after 3000 density to as close to 100 ROP then once in cruise, 50 ROP.  Are you saying this sounds too lean?

[OR75]

unfortunately, unlike cars, aircraft engines are air cooled.

[201er]

Something I discovered on my recent coast to coast Mooney cross country is that ROP yields far higher oil temps than LOP with all other things being equal (power, CHT, etc). I don't know why but 100ROP at high altitude cruise was sending my oil temps into the red and forcing me to open cowl flaps. Yet 10-40LOP and even back in some on the prop was keeping the oil temp at least 10F cooler.

[KSMooniac]

Quote: 201er

Something I discovered on my recent coast to coast Mooney cross country is that ROP yields far higher oil temps than LOP with all other things being equal (power, CHT, etc). I don't know why but 100ROP at high altitude cruise was sending my oil temps into the red and forcing me to open cowl flaps. Yet 10-40LOP and even back in some on the prop was keeping the oil temp at least 10F cooler.